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Astronomers Solve Magnetic Fields Mystery
An anonymous reader writes "It is a long-standing and unsolved mystery why 80% of all planetary nebulae are not spherical. Theories suggest that magnetic fields play a role in shaping planetary nebulae. A team of astronomers from Germany has now discovered the first direct clue that magnetic fields might indeed create these remarkable shapes. Planetary nebulae are expanding gas shells that are ejected by Sun-like stars at the end of their lifetimes."
Whatever would iron have to do with this? This is about plasma movement in a magnetic field. Or did you think star explosions ejected nice, neutral iron atoms? Here's a clue: the magnetic moment of iron is caused by its outer electrons.
On a solar system scale, the spin of the central body plays a large role in this, but it is still a kind of a game of chase-the-tail.
When the whole system is still gas, something starts it spinning -- a simple thing like a star passing nearby gives objects (the gas particles) a bit of angular moment, which is thus transferred to the system as a whole over eons of time through collsions, gravity, magnetic forces, etc.
Now, if a LARGE object passed by in the XY plane, and a SMALL object passed by in the YZ plane, you will end up with a spin *mostly* in the XY plane, but the *WHOLE SYSTEM* will balance out with a single plane of spin somewhere in between.
Eventually the smaller objects become larger objects, which collide less, thus distributing the angular moment less efficiently. There may be one central body spinning in the XY plane, but a few of the large objects can have a wildly different orbital plane. But not many objects will HAVE this wildly different orbital plane, because back when the system was being formed, the angular moment transfer WAS very efficient.
Also, 'circular' orbits, like the earths or mars or Jupiters, are fairly rare on a random scale of things; and if you have a bunch of objects orbiting in different planes with highly ellipical orbits, they have a much higher chance of smacking into each other (or some larger object, like jupiter) than the same object would if it were in a more circular orbit which happened to be in a different plane than that of the central masses spin. Don't forget the time scales in question here!
Now, finally, in systems like that of the Earth and its huge moon, you get tidal interactions; while the moon will never shift in its orbit enough to be in an equatorial orbit, it *does* shift more closely to one every day, thanks to the 'gravity drag' between itself and Earth. Really what is happening is that the Earths spin is accelerated in the direction of the moons travel (really, this is slowing our spin rate down, think acceleration in the physics sense). Earth has already done this to the moon; hence the 'tidal lock' which has the moon presenting the same side to Earth at all times.
Were you to watch the Earth moon system forever, eventually what you would see is two bodies rotating about a central point, both with the axis of spin of each body being parallel to the axis of rotation about said central point (hope you can visualise that!). In reality this won't occur in any amount of time, the influence of the sun, and the fact that the moon would actually leave earths gravitation influence before alignment could occur prevent it. (The orbit of the moon gets larger as it steals earths rotational momentum).
That was fun.